In WPF, under what circumstances does Visual.PointFromScreen throw InvalidOperationException?

Question

Suppose I wanted to do this, so I can find the current position of the mouse relative to a Visual, without needing access to a specific mouse event:

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Answer 1

I had a similar problem with a custom-made visual.

The solution was to defer the problematic task via Dispatcher (deferred execution with background priority in this case)...

public void MyProblematicDisplayMethod(Symbol TargetSymbol)
{
    this.HostingScrollViewer.BringIntoView(TargetSymbol.HeadingContentArea);
    ...
    // This post-call is needed due to WPF tricky rendering precedence (or whatever it is!).
    this.HostingScrollViewer.PostCall(
        (scrollviewer) =>
        {
            // in this case the "scrollviewer" lambda parameter is not needed
            var Location = TargetSymbol.Graphic.PointToScreen(new Point(TargetSymbol.HeadingContentArea.Left, TargetSymbol.HeadingContentArea.Top));
            ShowOnTop(this.EditBox, Location);
            this.EditBox.SelectAll();
        });
     ...
}

/// 

/// Calls, for this Source object thread-dispatcher, the supplied operation with background priority (plus passing the source to the operation).
/// 
public static void PostCall(this TSource Source, Action Operation) where TSource : DispatcherObject
{
    Source.Dispatcher.BeginInvoke(DispatcherPriority.Background,
        new DispatcherOperationCallback(delegate(Object state)
                                        { Operation(Source); return null; }),
        null);
}

I've used that PostCall in other ScrollViewer related rendering situations.